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1.
Mono-, di- and tri-alkyl-substituted allenes were potentiostatically oxidized in methanol at graphite and Pt anodes. At the former electrode, α-methoxylated ketones (due to 4F/mole electricity consumption) and esters (6F/mole) were the major products. At a Pt anode, intermediate products such as vinyl-ether derivatives (2F/mole) were characterised too. Unlike the anodic oxidation of alkenes and alkynes previously reproted in the literature, dimerisation is not a typical process in the allenes' oxidation, since of all the products obtained only a sole dimer has been observed. The mechanism for the formation of most products is discussed. 相似文献
2.
In this paper we report the results of an experimental study of the vacuum ultraviolet absorption spectra of molecular impurity states of methyl iodide in Ar (density range ? = 0–1.4 g cm?3) and in Kr (? = 0–2.3 g cm?3), of carbon disulphide in Ar (? = 0–1.4 g cm?3) and of formaldehyde in Ar (? = 0–1.25 g cm?3). The experimental results provide new information regarding medium perturbations of intravalenc transitions, of the lowest extravalence transitions and of transitions to mixed valence—Rydberg configurations, which serve as a diagnostic tool to distinguish between different types of electronic excitations. All the lowest extravalence molecular excitations exhibit appreciable blue spectral shifts at moderate and at high fluid densities, intravalence transitions are practically insensitive to medium effects, while excitations to mixed valence—Rydberg configurations are characterized by a moderate blue spectral shift. New information has been obtained concerning the energetics of molecular ionization processes in a dense fluid. The high n = 2–5 Rydberg states of CH3l exhibit a large red shift at moderate (? = 0–0.5 cm?3) Ar densities. The ionization potential Eg and the effective Rydberg constant G for CH3I in Ar was found to decrease from G = 13.6 eV and Eg = 9.55 eV at ? = 0 and Eg = 9.08 eV and constant G for CH3l in Ar was found to decrease from G = 13.6 eV and Eg = 9.55eV at ? = 0 and Eg = 9.08 eV and G ≈ 7.15 eV at ? = 0.5 g cm?3. Experimental evidence was obtained for the identification of n = 2 molecular Wannier impurity states of CH3I and of CH2O in liquid Ar. These spectroscopic data result in Eg ≈ 8.6 eV for CH3I in liquid Ar and Eg ≈ 10.2 eV for CH2O in liquid Ar. 相似文献
3.
The kinetics of the gamma-radiation induced free-radical chain reaction in solutions of carbon tetrachloride in cyclohexane (RH) has been investigated in the temperature range of 303–383°K. Trichloromethyl radicals were produced by the reaction of radiolytically generated cyclohexyl radicals with carbon tetrachloride. The kinetics of the following reactions were investigated: The following rate expression was obtained: The error limits are the standard deviation from the least mean square Arrhenius plots. Effects of phase on the kinetics of reactions (3) and (4) are considered. 相似文献
4.
Abstract— The chemiluminescence (CL) emitted during the peroxidase catalyzed oxidation of purpurogallin and pyrogallol depends on one and two molecules of enzyme, respectively. Using microperoxidase, CL with purpurogallin also depends on two molecules of enzyme (above 0.3 μ M enzyme). Sodium azide inhibits the CL emitted by all reactions depending on two molecules of enzyme but enhances the CL of reactions depending on one molecule of peroxidase (purpurogallin + 0.75 n M horseradish peroxidase). The formation of functional enzyme dimols during the oxidative process is discussed. 相似文献
5.
Light is shown to exhibit critical and tricritical behavior in passively mode-locked lasers with externally injected pulses. It is a first and unique example of critical phenomena in a one-dimensional many-body light-mode system. The phase diagrams consist of regimes with continuous wave, driven parapulses, spontaneous pulses via mode condensation, and heterogeneous pulses, separated by phase transition lines that terminate with critical or tricritical points. Enhanced non-Gaussian fluctuations and collective dynamics are present at the critical and tricritical points, showing a mode system analog of the critical opalescence phenomenon. The critical exponents are calculated and shown to comply with the mean field theory, which is rigorous in the light system. 相似文献
6.
Given a von Neumann algebra M and a W*-correspondence E over M, we construct an algebra H(E) that we call the Hardy algebra of E. When M= =E, H(E) is the classical Hardy space H of bounded analytic functions on the unit disc. When M= and E= H(E) is the free semigroup algebra studied by Popescu, Davidson and Pitts and many others. We show that given any faithful normal representation of M on a Hilbert space H there is a natural correspondence E over the commutant (M), called the -dual of E, and that H(E) can be realized in terms of (B(H)-valued) functions on the open unit ball ((E)*) in the space of adjoints of elements in E. We prove analogues of the Nevanlinna-Pick theorem in this setting and discover other aspects of the value distribution theory for elements in H(E). We also analyze the boundary behavior of elements in H(E) and obtain generalizations of the Sz.-Nagy–Foia functional calculus and the functional calculus of Popescu for c.n.c. row contractions. The correspondence E has a dual that is naturally isomorphic to E and the commutants of certain, so-called induced representations of H(E) can be viewed as induced representations of H(E). For these induced representations a double commutant theorem is proved.Supported in part by grants from the National Science Foundation and from the U.S.-Israel Binational Science Foundation.Supported in part by the U.S.-Israel Binational Science Foundation and by the Fund for the Promotion of Research at the Technion.Revised version: 11 March 2004 相似文献
7.
It is shown that additive noise can inhibit modulation instability in laser equations of motion. A related self-starting condition for pulsation is obtained by employing a fluctuation--dissipation relation between noise and losses and a statistical mechanics approach. Entropy considerations are shown to play a crucial role. The quantum limit for self-starting is estimated. 相似文献
8.
Monodisperse granular flows often develop regions with hexagonal close packing of particles. We investigate this effect in a system of inelastic hard spheres driven from below by a "thermal" plate. Molecular dynamics simulations show, in a wide range of parameters, a close-packed cluster supported by a low-density region. Surprisingly, the steady-state density profile, including the close-packed cluster part, is well described by a variant of Navier-Stokes granular hydrodynamics (NSGH). We suggest a simple explanation for the success of NSGH beyond the freezing point. 相似文献
9.
Baruch Karp 《International Journal of Solids and Structures》2011,48(1):126-136
The dynamic response of an elastic, semi-infinite strip with sliding surfaces, subjected to various forms of end excitations, was solved analytically employing the property of bi-orthogonality of wave modes. An explicit relation between the amplitudes of evanescent waves and the form of the excitation was obtained. Quantitative measure for dynamic end effects was suggested, termed Saint-Venant ratio (SVR). It was shown that two qualities of that ratio are useful for monitoring the health of structural joints (SHM): being that ratio not affected by the intensity of the end excitation and its high sensitivity to small variations in the form of the excitation. The axial behavior of the strip subjected to several forms of end excitations was further used to demonstrate the validity of a previously suggested dynamic version of Saint-Venant’s principle. 相似文献
10.
David Levanony Menahem Baruch 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》1987,38(6):874-882
The behaviour of a non-uniform beam loaded by a parallel or tangential compressive force respectively is analyzed by exploiting a two-degree-of-freedom dynamic model. The same system has been analyzed previously by Lee and Reissner from a static point of view and by Neer and Baruch by a dynamic approach using a one-degree-of-freedom model. The previous analyses revealed only part of the phenomena by the present approach.Here, for the tangential force a classical flutter instability is obtained and for the parallel force only static instability is possible. 相似文献